I believe so. And we will have to prepare ourselves for long tail keywords as well.
More that smart devices at home, I think Google Assistant, Cortana, Siri etc will be the most traffic routing assistants through mobile. People don't want to type anymore. And voice typing has gone easy.
I think it is unwise to ignore Alexa. Amazon is selling a lot of home devices. They have a whole series of it, with and without video. You will have to work on your structured data scheme to make sure that it reads out your solution.
Agreed on that point. Alexa powered devices or smart home devices are not too many in number. Also, they work with other smart devices. So maybe other than weather, most of them would be switch on the lights, increase the volume etc